Master cylinder piston for hydraulic brake systems



Dec. 6, 1932. J. R. HEIDLOFF 1,889,987

MASTER CYLINDER PISTON FOR HYDRAULIC BRAKE SYSTEMS Filed Aug. 18. -1930 445 the following description with reference to Patented Dec. s, 1932 i 1,889,987

UNITED STATES PATENT OFFICE- JOSEPE R. HEIDLOFF, F DETROIT, iIICHlGAN, ASSIGNOR TO HYDRAULIC BRAKE COMPANY, OF DETROIT, MICHIGAN, A CORPORATION' 0F CALIFORNIA MASTER. CYLINDER. ris'roN ron. HYDBAULIG Bnnxn SYSTEMS Application mea August is, 1930. semi No. 475,972.

The invention relates to hydraulic brake which contains the improved master piston systems and more particularly to an imof my invention; provement in the master cylinder associated Fig. 2 is a fragmentary sectional view of therewith. the forward end of the master cylinder show- In a hydraulic braking system such as ing the position of the master piston and its 55 illustrated in an application of Malcolm associated parts during the retractile move- Loughead, Serial No. 304,195, led Septemment of the same; ber 6, 1928, and issued on March 1, 1932, as Fig. 3 is avfragmentary sectional view of Patent No. 1,847,402, the master cylinder the master cylinder illustrating a modified piston is arranged with a series of holes to form of master piston; and 60 provide a passage for iuid from the rear of Fig. 4 -is a sectional view along the line the piston and around the base of a packing 4 4 of ig. 3 looking in the direction of the cup associated with the piston upon the rearrows indicated thereon.

tractile movement of the same. The pack- Referring to the drawing and particularly 5 ing cup is firmly seated against-the piston to Figs. 1 and 2, the housing2 containing the 65 during the pressure stroke of the same and master cylinder 3`with which the master cylthere is a likelihood, particularly under high indelj plston of my invention is associated braking pressures, of the cup material being 1s suitably attached to the frame of an autoforcod into those holes which Wouldhinder mobile and constitutes a reservoir which the proper passage 0f Huid through these Under IlOImal COIlditiOl'iS Stands full 0f liquid 70 holes and in extreme instances would cause t0 about the level as indicated at 4. the ruination of the packing cup. To ob. An operating shaft 5 is journaled in the viate this condition I have devised a novel OPPOSlte Walls 0f the housing 2 and carries an Ingang of protecting the, packing cup and external iGVeI Which S t0 the OO an object of my invention is the provision brake ped'll O f the automobile (not shown). 75 0f an improved master cylinder piston, A. IOVGI 6 1S llgldly SQCuIed l130 the Shaft 5 A further Object is l15() provide a, master 8, boit 7 Wltlllll the hOllSIlg 5 8.116. has 8. hOOkcylinder having a master piston provided Shaped @11d 8 Serving to transfer the rotary with a packing cup having moons interposed motion of the shaft 5 tothe piston indicated between the cup and the piston which pregenerally by the reference Character 9 and vent direct contactual engagement between OPGIS-llg Wthln the master cylinder 3. The the cup and the piston, .y master cylinderBhas threaded enga ement at A further object is to4 provide a master 10 with one end of the housing 2 an is therepiston in Combination with o, packing @up by rigidly heldinplace in a horizontal posiand a protective disc interposed between the tlfm- The reselyollf 01' housing 2 is POVided cup and piston which is most positive in its Wlth a Cover l; Whlch Supports@ llmg cap operation to interrupt communication be- 12 find, cqmpflses a' double atmg Valve 13 tween the master cylinder and the fluid reser- Whlch 1s UeldWgIy h eld 0n theh0u1de1` 14 by o voir during the pressure stroke of the piston mleans 0 a C011 Sprmg 15 Whlch enga es a 90 and to admit fluid into the cylinder during glite 16 xeduon the upper edge 17 0 the the return stroke of the piston. ng Clap wat18 h 1d t The above objects, as well as others not Va Ve Sea e in posmon betwien )arti-cular, Onted out will ear fr m the end of the master cylinder 3 and the side l y P a 2|'PP o 19 of the rleservoil11'2, cooperates with a double actin va ve 2O avin a assa ewa therethfe accommlymg d mwlng 1n Whfch 11k@ througgh which is normtliillylblose by ii, second re @rence c iai actors in the several views de- Valve 2L The volvo 21 is held in place by a not? like PItS and 1n. Wh'lch spring 22 which exerts a pressure longitudi- Fig. 1 is a longitudinal section taken nally on a pin 23 through the medium of its through the reservoir and the master cylinder head 24. As the double. acting valve 20 forms 100 no part of my invention a detailed description of its operation will not be given, suice to say that it is actuated by movement of the piston 9 in the master cyllnder 3 to regulate the pressure within the linesand the wheel c linders of the brakes and to control the ow of brake fiuid from and to the master cylinder 3 upon the compression andsuction strokes of the piston 9 mounted therein. A suitable drain plu 25 is provided in a tapped opening 26 in the ottom of the reservoir for permitting the same to be drained from time to time as required.

The master piston 9 of my invention comprises a face portion 27 provided with a counterbore 28 and a rearwardly extending flange 29 and a centrally located rearwardly extending lug 30 provided with a central bore 31 into which is fitted a wear piece or stud 32 having a head 33 on its outer end adapted to be engaged by the hooked end 8 of the actuating lever 6: AThe free or piston end of thel master cylinder 3 is provided with a groove 34 in which is fitted a C-shaped spring retaining member 35 adapted to be engaged by the annular edge of the flange 29 of the master piston 9 when inits normal position.

A rubber packing cup 36 is associated with the master piston 9 and comprises a flat discshaped portion 37 surrounded by a peripheral flange 38 extending axially from the discshaped portion '37 and is provided with a plurality of spaced grooves`39 extending in an axial direction toward the piston 9. A disc washer 40 provided with a beveled or tapered edge rests against the face 41 of the discshaped portion 37 of the cup 36 under the influence of a helical spring 42 resting in the bore 31 in the piston 9.

The cup 36 and washer 40 are urged into the position illustrated in Fig. 1 with the washer 40 extending into the counterbore 28 in the face 27 of the piston 9 by a retractile spring 43 which has one'end rest-ing against acup-like spring retainer 44 bearing against the cup 36 and receives and holds in position this end of spring 43. The opposite end of the spring 43 'bears against the valve 20 to normally retain the valve 20 in contact with .Y its seat 18. The retainer 44 is provided with a plurality of openings 45 for the passage of brake fluidpast the retainer.

The light compression spring 42 resting Within the central bore 31 of the piston 9 has its one end engaging. the face of the Washer 40 and its other end engaging the plug 32 in the piston and acts Ito force the piston 9 away from the cup 36 and washer 40 upon the return stroke of the piston, as will be more clearly hereinafter described.' The` master cylinder 3 is provided with an opening 46 which communicates with the interior of the cylinder immediately forward of the inner end of the acking cup 36 which permits luid from t e reservoir to pass direct- ,tem into the cylinder.

ly into or out of the master cylinder when t e piston 9 is in its normal position, as illustrated in Fig. 1. The piston 9 is provided with a duct 47 through the central lug 30 to the rear side of the piston 9 and communicates Withthe central'bore 31 so that upon the return -movement of the master pistn 9 under the influence of the retractile spring 43 fluid will pass through the duct 47 and bore 31 and by the peripheral flan e 38 of the packing cup 36 as will present y be described.

In the operation of the apparatus thus described the movement of the master piston 9 into the master cylinder 3 under the influence of the lever 6 causes a fluid pressure in the master cylinder 3 to unseat the valve-21 and permit fluid under pressure to pass through the outlet 48 into the brake system. The

pressure in the master cylinder 3 forces the counterbore 28 and asv the diameter of the bottom face 80 of the washer 40 is substantially that of the counterbore 28, this bottom face 80 of the washer 40 and the annular portion of the face 27 of the piston 9 forms a substantially flat continuous face against which the face 41 of the packing cup 36 is forced under the influence of the fluid pressure in the cylinder 3 which prevents cutting of the -cup 36 by the inner peripheral edge of the counterbore 28.

Upon the return movement of the piston 9 under the infiuence of the spring 43, the fiuid pressure within the cylinder 3 will decrease on account of the check valve 20 which retards the return flow of fluid from the sys- The reduced pressure in the 'cylinder 3 is also aided by a partial vacuum created in the cylinder as the spring 43 forces the p iston 9 to its retracted position, and the spring 42 in the bore 31 of the pistonv9 now acts to force the piston 9 away from the washer 40 and cup 36. The

fluid pressure in the reservoir 2,. which is the same at all times, now becomes greater than the fluid pressure in the cylinder 3 during the retractile movement of the piston, allowing the fluid from the reservoir 2 to flow through the duct 47 and bore 31 and the passage 70 around the base of the washer 40 and cup 36, whichpassage 70 permits the free passage of fluid, as clearly illustrated in Fig. 2, past the packing cup 36. The grooves 39 in the packing cup 36 facilitatelthe passage of liquid past the packing cup- 36 and as the flange 38 of the same is fiexible it is flexed nesacev s 3 inivarldly to unseat the dan e from engagement with the Walls of the c. inder 3.

In this manner, at the en of the retractile movement oi the piston 9 there is a greater quantity of Huid in the cylinder 3 and in the system than is necessary for the operation of same, and continued flow of fluid from the system as the wheel cylinder pistons move to their retractile position, will cause all excess uid in the cylinder 3 to pass up through the small passage 46 in the cylinder wall to the reservoir 2. When the piston 9 is in its ully retracted osition and the iuid pressure in the c lin ver 3 and reservoir 2 are equal, the spring 43 again forces the Washer 40 into the counterbore 28 in the head of the piston 9 to again compress the spring 42 in the bore 3i.

t is most eential that the area ci the duct opening 47 be greater than the area ot the passage around the base or the cup 36 and washer 4() caused by the movement of the piston 9 under the infiuence of the spring 42, as before pointed out, to overcome the tendency of the piston 9 to adhere to the washer 40 due to the partial vacuum created on the pressure side of the piston as the same is retracted under the induence of the retractile spring 43. With the area of the duct 47 suiiiciently large the Huid pressure from the reservoir 2 through the duct 47, in combination with the effort of the spring 42, will overcome this adhesive tendency to permit the p roper function of the packing cup 36 at all times.

The bleeder passage which includes the bore 31 is located centrally in the piston 9 and is covered by the washer 40 during the protractile or pressure stroke of the piston 9 so that under braking pressure no portion of the packing cup 36 covers this bleeder passage, which eliminates the possibility of the forcing of the cup material into the bore 3l.

ln the modification illustrated in Figs. 3 and 4 fragmentary sections of the master cylinder, piston 9 and the packing cup 36 are shown. The member interposed between the cup 36 and piston 9 is in the form of a disc having four integrally formed lugs 7' 6 depending therefrom. The length of the lugs 76 is the same as the depth of the counterbore 28 in the face 27 of the piston 9.

The disc 75 rests against the face t1 of the disc-shaped portion 37 of the cup 36 under the influence of a helical spring 42 resting in bore 3l of the piston 9 and maintains the disc 7 5 in contactual engagement with the cup 36 at all times. Upon the protractile movement of the piston 9 a pressure is produced in the cylinder 3 and upon the retractile movement of the piston 9 the spring 42 acts to force the piston 9 away Jfrom the disc 7 5 and cup 36, as previously described` and fluid from .the reservoir passes through the duct 47 and bore 31 around the base of the disc 75 and cup 36, permitting the tree passave of fluid past the packing ou 36.

l@The operation and function o the disc 75 in combination with the packing cup 36 is the same as previously described in connection with Figs. l and 2, but in the modification shown the depending lugs 76 do not permit eontactual engagement between the disc 75 and the bottom of the counterbore 28 to eliminate the adhesive tendency upon the retractile movement or the piston 9.

While l have illustratedand described my invention for a particular use, it is to be understood that the piston of my invention is applicable for other uses, and changes and modifications' may be made, but l am to cover all such changes as come within the spirit and scope of the appended claims.

What l claim as new and desire to cover by United States Letters Patent is:

, l. iin mechanism of the class described, the combination of a cylinder, a piston reciprocable thereima packing cup adjacent the for- Ward face of said piston, a fluid supply in communication with the rear of said piston, said piston having a passageway therethrough, and a movable member for preventing said packing cup from being forced into said passageway during the protractile stroke of said piston.

2. ln a hydraulic brake mechanism of the class described, the combination of a cylinder, a piston reciprocable therein, a fluid supply to the rear of said piston, a packing cup associated with the forward face of said piston around the region of said passageway through said piston, and a member engaging said cup and movable therewith for preventing said packing cup from engaging sa'd piston around the region of said passageway during the protractile stroke of said piston.

3. In a hydraulic .brake mechanism ofthe class described, the combination of a cylinder, a piston reciprocable therein. a packing cup associated with the forward face of said piston, a fluid supply to the rear of said cylinder, means engaged by said cup and co.

operating with said piston to provide a continuous Jdatcontacting face for said cup during the nrotractile movement of said piston, and spring means for moving said means and said cup relative to said piston upon the retractile movement of the piston to permit luid to flow past said cup;

4. n a hvdraulic brake mechanism of the class described, the combination of a cvlinder, a piston reciprocable therein, a packing cup associated with said piston. a iuid supply to the rea-r of said piston. a passageway extending through said piston, a member engaging lsaid cup, and a counter-bore in said piston for receiving said member to provide a fiat contacting surface for said cup during the protractile movement of said iston, said member preventing said cup from cmg forced into sal passageway durmg said movement.

5. In a h draulic brake mechanism of theI class descri ed, the combination of a cylinder, a piston reciprocable therein, a p acking cup associated with said piston, a fluid supply to the rear of said piston, a passageway extending through said piston, a member engaging said cup, a counter-bore in said piston for receiving said member to provide a fiat contacting surface for said cup during the protractile movement 'fof said piston, said member preventing said cup from contacting said piston in the environs of said passageway, and spring means for moving said piston4 relative to said member and cup during the retractile stroke thereof to permit fluid to flow past said cup.

6. In a hydraulic brake mechanism of the class described, the combination of a cylinder, a piston reciprocable therein, a fluid on both sides of said piston, a Huid passage in said piston, a packing cup adjacent the forward face of said piston, means interposed between said cup and piston to provide a smooth contacting surface for said cup during the protractile stroke of said piston, and spring meansfor separating said cup and said means from said piston during the retractile stroke of said piston to provide an annular passage between said piston and said cup and said means to allow iuid delivered through said uid passage to pass forwardly past said cup.

7 In a hydraulic brake mechanism of the class described, the combination-of a cylinder, a. piston reciprocable therein, a fluid on both sides of saidpiston, a fluid passage in said piston, a packing cup adjacent the forward face of said piston, a disc interposed between said cup and piston, a counter-bore in the forward face of said piston for entry of said disc to provide a smooth contacting surface for said cup during the protractile stroke of said piston, and spring means for moving said piston relative to said cup and disc during the retractile stroke of said piston to provide an annular passage between said piston and said cup and disc to allow Huid delivered through said fluid passage to pass forwardly past said cup.

8. In hydraulic brake mechanism of the class described, the combination of a cylinder, a piston reciprocable therein and affording a. fluid passageway therepast, a source of fluid supply in communication with the rear of said piston during the retractile stroke thereof, a packing member associated with the forward face of said piston to form a fluid-tight seal during the protractile stroke thereof, and means cooperating with said piston to provide a support for said packing member during the protractile stroke of said piston and movable relative to said piston `said cuppacking during the forward stroke of the piston, sald member being actuated by said cup packing during the forward stroke of the piston toclose said recess, and permitting Huid to How past said piston durmg the return stroke thereof.

10. In mechanism of the class described, the combination of a cylinder, a piston reciprocable therein, said piston havlng a assage therethrough terminating at one en in a recess formed in the face of the piston, a member adapted to fit in said recess, said member when so pisitioned having a forward face lying in the plane of the forward face of the piston, means for reciprocating said piston, a packing cup adjacent the forward face of said piston, and means including eooperating surfaces on said piston and member for centering said member relative to the recess in said piston.

11. In mechanism of the class'described, the combination of a cylinder, a. piston reciprocable therein, said piston having a assageway therethrough, a packing cu a jacent the forward face of said piston, t e rear face of said piston being in communication with a body of Huid, and a member closin said passageway and providing a seat for said packmg cup during the forward stroke'of said piston, said member movable relative to said piston and having centering means extending into said passageway.

12. In mechanism of the class described the combination of'a cylinder, a piston reciprocable therein, said piston having a recess in its forward face and being provided with a Huid passa feway between said recess and the rear of saidpiston, there being a body of fluid in communication with the rear of said piston, a' self-centering member for closing said recess during the forward stroke of said piston and movableD therefrom during the return stroke to permit flow of Huid past said piston, and a relatively'soft packing member adjacent the forward face of said piston for moving said self-centering member to close said recess during the forward stroke of said piston.

In witness whereof, I hereunto subscribe my name this 14 day of Aug., 1930.

JOSEPH R. HEIDLOFF.

CERTIFICATE OF CORRECTION.

Patent No. 1, 8,89, 987. December 6, 1932.

JOSEPH- R. HEIDLOFF.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, line 102, claim 2, strike out the words "around the'region 0f said" and insert instead "and movable therewith, a"; andthat the said Letters Patentshouldbe read with this4 correction thereinthat the same may conform to the recordof the case in the Patent Office.

Signed and sealed this 14th day of February, A. D. 1933.

- M. J. Moore, (Seal) ActingV Commissioner of Patents. 

